The objectives of the proposed research are to establish a correlation between variations in apolipoproteins and various human diseases which lead to premature atherosclerosis. These objectives will be realized by further study of a) the structure and function of normal and variant apolipoprotein genes, and b) the biochemical events which control the synthesis and secretion of human apolipoproteins. The specific aims of the proposed research are: 1) To determine the structure and regulation of expression of human apolipoprotein B; 2) To study the structure and regulation of expression of the apoE gene obtained from patients with plasma apoE deficiency and compare it with the normal apoE gene; 3) To determine cis-acting elements or transacting factors which control the expression of apolipoprotein genes; 4) To study the post translational modifications of apolipoproteins and their importance for lipoprotein metabolism. The structure of human apolipoprotein B will be determined from the DNA sequence of overlapping Agt10 apoB cDNA clones. The structure of the apoE deficient gene will be determined with conventional techniques and the function of the cloned genes will be measured using transient and stable eukarvotic cell expression systems. The synthesis and post translational modificaitons of apolipoproteins will be studied in intestinal cell lines. The importance of the segments of apolipoproteins involved in post translational modification will be determined by site directed mutagenesis. The cis-acting elements or transacting factors involved in the expression of apolipoprotein genes will be assessed by expression studies of appropriately mutagenized human apolipoprotein genes. The findings of the proposed studies would be very important from a public health standpoint. Abnormalities in lipoprotein metabolism contribute significantly to coronary atherosclerosis and heart disease. The development of atherosclerosis could be retarded if the molecular bases of the diseases which lead to it were known and tests were available to diagnose these diseases early in life. The proposed research will enhance our knowledge of new molecular aspects of lipoprotein metabolism which may be relevant to human diseases and will contribute towards better diagnoses and treatment of these conditions.